This application relates generally to a gas turbine engine for an aircraft, and more specifically, to a reverse flow gas turbine engine that contains an airflow bypass.
Jets and aircraft powered by gas turbine engines typically have small auxiliary engines at the back end, often referred to as auxiliary power units (APUs). These engines often have no fan, and are considered low pressure ratio devices. The APU provides ground power to operate cabin systems, such as the environmental control system (including air conditioning) and powering the electronics of the aircraft cabin, as well as provide start-up potential for the flight engines. APUs currently are parasitic hardware, i.e., the unit is used on the ground, but it is seldom used in flight. Thus, most APUs are considered waste weight on an aircraft. Typical APUs may generate enough ground power, but flight engine cores are also actuated often on the ground. APUs typically turn off automatically when flight engine cores are activated.
With the cores getting smaller in large pressure ratio geared turbofan engines, the core size for a single isle jet or aircraft is similar to the prior art APU. Elimination of the APU from an aircraft is desired to save weight, and thus fuel burn which is in direct proportion to the weight of a jet or aircraft.